Avifaunal assemblage in Mt. Hamiguitan, Davao Oriental, Mindanao Island, Philippines
A positive relationship between avifaunal distribution and vegetation may be interrupted by habitat disturbances as environmental stresses. Hence, general pattern of avifaunal distribution across elevational gradients was qualitatively characterized. Vegetation ranging from lowland, montane and mossy forest was explored for bird utilization. A combination of participatory line- transect survey and mist-netting technique were used to sample bird species in eight sampling sites in Mt. Hamiguitan Range from July 2006 to March 2007. There were a cumulative of 53 species of birds assigned to 26 families and 11 orders. Twenty species (37.8%) of which are Philippine endemics and 10 species (18.9%) are confined in Mindanao. With the altitudinal isolation of vegetation, the number of species, abundance and endemism increase as elevation decreases. Hence, there is a direct relationship between vegetation and niche breadth of birds. Thus, the higher affinity of the location of vegetation, the greater number of similar species occurred between them. Species of birds are highly similar between proximate habitats like lowland dipterocarp forest and montane forest as well as montane and mossy forest than in vegetation with greater elevational gradient. Therefore, communities of birds with reference to diversity, abundance and endemism are distributed based on vegetation at increasing elevation in a tropical rainforest.
Keywords: vegetation, endemic species, elevation, biodiversity, avifauna